Reference Level

The sea Level data are given with respect to 'ASCENSION B-DATUM MAY 1993' until 1998, then with respect to 'ASCENSION B-DATUM MARCH 1999'. The new datum is known relative to the old datum through levelling and is 6.4 cm ABOVE the old datum.

Quality Assessment

All data have been tidally analysed and constants and residuals checked. Records have been visually inspected for spikes, timing and datum shifts.

In the series 1999-2000 and 2000-2001, the half tide sensor records values about 0.3 decibars below the sub surface (total) pressure sensor.